The present invention relates to a method for manufacturing face-to-face woven pile fabrics, two backing fabrics being woven above one another on a weaving machine by inserting weft yarns in successive weft insertion cycles between binding and tension warp yarns, the pile warp yarns forming a pile in at least one part of the pile fabric by being alternately interlaced around a weft yarn in the upper backing fabric and around a weft yarn in the lower backing fabric and pile warp yarns forming no pile in at least another part of the pile fabric and being interlaced in one of the backing fabrics in accordance with a predetermined pattern. More particularly, the present invention is relating to a high density pile fabric manufactured in accordance with the present method.
Furthermore, the present invention relates to a weaving machine provided for the method according to the invention to be carried out.
Hand-knotted fabrics are characterized by:                a high density;        a delicate design in many colours (six colours and more);        a nice back.        
When weaving there is an evolution to systematically increase the density of pile fabrics. Where in weaving, the weaving reed used to be a restriction for densities above 550 pile warp yarns per metre, because the number of reed dents per metre was restricted to 550, the European patent publication EP 1 347 086 proposes a method for the densities of a pile fabric to be increased by providing two pile warp systems per reed dent in combination with a suitable arrangement of the backing warp yarns in this reed dent in order to realize a certain separation between the pile warp yarns of the two pile warp systems within the same reed dent.
In this manner, it will be possible to produce fabrics having 700 and even 800 pile warp systems per metre in the weft direction. It is possible to apply this method with 1/1 V-weave as represented in EP 1 347 086 on a double rapier weaving machine, the pattern forming pile warp yarn being interlaced alternately in each fabric around a weft at the back of the fabric and then around a weft on the pile face of the fabric.
With this method therefore, only half the pile will be interlaced around a weft at the back of the fabric, so that the other half of the pile will be interlaced less securely on the pile face of the said fabric, which may be deduced immediately from the pattern which will be observed at the back of the fabric. This pattern will contain only half of the pile points and therefore is less delicate than the pattern at the front of the fabric.
In a 1/2 V-weave all pile warp yarns are indeed interlaced around a weft at the back of the fabric. Here, the pile warp yarns being interlaced securely, which is clearly shown by the pattern at the back of the carpet. The pattern at the back clearly corresponds to the pattern at the front, because of which, a quality may be approached which will be better in accordance with a hand-knotted carpet than the one of a 1/1 V-weave which is not fully interlaced through to the back of the fabric.
Only, when weaving the 1/2 V texture by means of the multiple rapier technique, the problem may occur that mixed contours are produced, preventing delicate designs from being formed, which is rather inconvenient in fabrics of this density.
Mixed contour mean that two pile tufts of a different pile warp yarn (colour) will occur between two successive wefts in a face-to-face fabric, which will be crossing and standing upright next to one another in a face-to-face fabric. Because the two pile tufts are crossing with this colour change, they will take up a wrong position with respect to one another in accordance with what is desired and this will cause the pattern of the fabric to become indistinct.
It is known that certain mixed contours may occur in one of the fabrics or in both fabrics at certain colour (pile warp yarn) changes, dependent on the positions taken up by the yarns of these changing pile warp yarns when they are not forming the pattern and are interlaced as dead pile. Thus:                when the pile change occurs from a pile warp yarn being interlaced as a dead pile in the upper fabric, to a pile warp yarn being interlaced in the lower fabric, a mixed contour will never be produced;        when the pile change occurs from a pile warp yarn being interlaced as a dead pile in the upper fabric, to a pile warp yarn being interlaced in the upper fabric, a mixed contour will be produced in the upper fabric;        when the pile change occurs from a pile warp yarn being interlaced as a dead pile in the lower fabric, to a pile warp yarn being interlaced in the lower fabric, a mixed contour will be produced in the lower fabric;        when the pile change occurs from a pile warp yarn being interlaced as a dead pile in the lower fabric, to a pile warp yarn being interlaced in the upper fabric, a mixed contour will be produced in both fabrics;        
Such mixed contour effects may be avoided by providing two lines of the same colour (the same pile warp yarn) in the card design after one another and to apply to them the method described in the European patent publication EP 9 27782 and, of at least one of the pile warp yarns involved in the pile change, one lift plan before the pile change or one lift plan after the pile change being replaced by a correction lift plan.
In practice, such correction lift plans may be applied automatically to the processing software transforming the design into a file in order to activate the Jacquard machine. However, in order to be able to apply this method, a number of rules have to be respected as indicated when setting up the design, namely that the correction lift plan may only be applied to produce the effect expected, when during two successive pile plans the pile is formed by one and the same pile warp yarn.
In the very delicate patterns to be woven by means of the devices as described above, applying these applications to the design is very labour intensive. Moreover, the liberty of designing in delicate drawings will be restricted.
Moreover, the fact of mixed contours occurring or not, depends on the position of the pile warp yarns in the weaving creel, for the position of the pile warp yarns will determine in which fabric the pile will be interlaced.
Although, from a technical point of view, it is possible to avoid mixed contours, we find that in practice, quite some fabrics are still showing mixed contours. Moreover the delicate designing requires (typical of fabrics imitating hand-knotted carpets) a freedom of designing, which is not always to be realized by avoiding mixed contours as described above. Double colour rows in order to avoid mixed contours are sometimes inconvenient to the delicacy of a design.
The 1/1V method and the 1/2V method as described before, moreover, have the disadvantage that they are restricted to about 40 pile warp yarns per centimetre with double rapier weaving machines which are normally used.
At higher densities of pile warp yarns, there will be problems as to the perfectness of the quality of the back and the dead pile protruding from the back of the fabric. This certainly is the case with acrylic and woolen yarns having a surface which is more coarse. With polypropylene yarns also, which are smoother, these problems will occur, but in that case rather from 42 to 45 pile warp yarns per centimetre.
This means, that a fabric having a high density and many colours will cause problems to be woven, both with a 1/1V and 1/2V weave, on a double rapier weaving machine in the following structures:                600 pile warp systems per metre in 7 chore and more:        700 pile warp systems per metre in 6 chore and more:        800 pile warp systems per metre in 5 chore and more.        